A frequency-domain conversion unit (21) converts an input signal to a frequency-domain signal and outputs the result. A first noise removal unit (22) applies noise removal to a high-frequency-component signal having frequencies equal to or higher than a predetermined frequency in the frequency-domain signal output from the frequency-domain conversion unit (21) and outputs a resultant first converted signal. An encoding unit (23) encodes the high-frequency-component signal on the basis of the first converted signal and writes an encoded signal into a storage device (24). A decoding unit (25) reads the encoded signal from the storage device (24), decodes the encoded signal, and outputs a decoded signal. A second noise removal unit (26) applies noise removal to the decoded signal and outputs a signal from which noise has been removed. A frequency-domain inverse conversion unit (27) converts the signal output from the second noise removal unit (26) to generate a signal in which noise is removed from the input signal.
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